The long-range goals of this proposal are to develop robust and reproducible methods for ovarian tissue cryopreservation and transplantation as options for fertility preservation in survivors of cancer or other benign conditions wherein ovaria function is compromised. While 80% of young patients currently survive their cancers, devastating side effects of chemo- or radiotherapies leave female survivors facing infertility due to ovarian failure. Cryopreservation of ovarian tissue remains the only option for prepubertal, adolescent and young women with cancer as well as adult patients for whom immediate cancer therapy is required. But, human ovarian tissue cryopreservation is considered experimental and hampered by several factors. Embryology clinics in the U.S. favor embryo and oocyte vitrification over slow-rate freezing, but there is no uniform protocol for vitrification of ovaria tissue. Although 30 human births have been reported from slow-rate freezing and transplantation to orthotopic sites, only 4 could claim that the transplanted tissue was known to be the source of the oocytes. Most young survivors will not have a healthy ovarian vascular bed as a transplantation site following cancer therapies. Cryopreservation is also the only option for patients contraindicated for ovarian transplantation due to the risk of reintroducing malignant cells. While in vitro follicle culture is under development, most studies use follicles isolated frm non-cryopreserved tissues. We successfully devised a method for vitrification of rhesus monkey ovarian tissue in a closed system, and demonstrated post-thaw function in vivo and in vitro. When transplanted to heterotopic sites, vitrified tissue resumes ovarian function, and yields mature oocytes capable of preimplantation embryonic development. Secondary follicles isolated from vitrified tissue and encapsulated for 3-dimensional (3D) culture survive, grow to antral stages and produce steroid hormones in vitro, but oocyte quality is poor. Since the ovarian cortex is composed of complex cell types that complicate cryopreservation, vitrification of individual follicles and subsequent 3D culture is a novel approach toward preserving gametes for young patients with highly invasive cancers. An elite panel of co-investigators and collaborators that bring expertise in both state-of-the-art cryobiology as well as pre-eminent experience in clinical ovarian transplantation will help us advance the current technology for more rapid translation to clinical practice for patients. Using the rhesus monkey, we propose to identify the transplantation site for optimal fertile function of both prepubertal and young adult ovarian cortical tissue, improve long-term transplant function via local administration of factors important for revascularization as well as follicular survival, and optimize vitrification of isolaed preantral follicles and their ability to yield competent oocytes following 3D culture in vitro. Liv births in nonhuman primates after these controlled studies will establish the safety and feasibilit of experimental therapies prior to clinical translation so girls and young women can be offered the best chances of becoming mothers after surviving cancer.